As you draw cable tray, Revit automatically adds fittings. Use the following procedure to manually add cable tray fittings to an existing segment or run. 
-  Click Systems tab
Electrical panel
 Cable Tray Fitting.  
- From the Type Selector, select the cable tray fitting type that you want to place. 
Tip: On the 
Options Bar, you can specify that the fitting rotate as you place it. 
 
  
- In the drawing area, click the endpoint of the cable tray segment where you want to place the fitting. 
 
 
- To finish, click Modify.